<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>

<body>
    <div id="app">
        <!-- 全选框 -->
        <label for="allChecked">全选</label>
        <input type="checkbox"
         id="allChecked"
         @change="allSelectFn" 
         :checked="isAllSelect">
        <!-- 购物车列表 -->
        <ul>
            <li v-for="(item,index) in dataArr">
                <input type="checkbox"
                 :checked="item.checked"
                  @change="changeSelectFn(item)">
                商品名称: <span>{{item.name}}</span> |
                商品单价: <span>{{item.price}}</span> |
                数量: <input type="number" min="1" v-model="item.num"> |
                小计: <span>￥{{item.num*item.price}}</span>
            </li>
        </ul>

        <span>总价:¥{{total}}</span>
    </div>

    <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>
    <script>
        let vm = new Vue({
            el: "#app",
            data: {
                isAllSelect: false,
                dataArr: [{
                    id: 1,
                    name: "iPhone14",
                    price: "5999",
                    num: 1,
                    checked: false
                },
                {
                    id: 2,
                    name: "iPhone14 Pro",
                    price: "7999",
                    num: 1,
                    checked: false
                },
                {
                    id: 3,
                    name: "iPhone 14 Pro Max",
                    price: "8999",
                    num: 1,
                    checked: false
                }
                ]
            },
            computed: {
                total() {
                    let sum = 0;
                    this.dataArr.forEach(item => {
                        if (item.checked) {
                            sum += item.num * item.price;
                        };
                    })
                    return sum;

                }
            },
            methods: {
                allSelectFn() {
                    this.isAllSelect = !this.isAllSelect;
                    this.dataArr.forEach
                    (item => item.checked = this.
                    isAllSelect);
                }
            },
            changeSelectFn($item) {
                $item.checked = !$item.checked;
                let res = this.dataArr.some
                (item => !item.checked)
                if (res) {
                    this.isAllSelect = false;
                } else {
                    this.isAllSelect = true;
                }
               
            }
        })
    </script>
</body>

</html>